1. Field of the Invention
The present invention relates to a lid latch mechanism for a clean box for transferring and reserving various articles to be processed such as semiconductor wafers in a clean condition in a process for manufacturing semiconductors, electronic part related products, optical discs or the like.
2. Related Background Art
Recently, in a manufacturing process that requires a high level clean environment such as a semiconductor device manufacturing process, a method such as a mini-environment or a local clean space where an entire factory is not kept clean but only the ambient environment for products is kept under a clean condition has been adopted. In brief, only the interior of the respective processing apparatus is kept clean, which is used in the manufacturing process, and the transfer and reservation of the articles to be processed between the respective processing apparatus (clean apparatus) are performed by using containers (i.e., clean boxes) whose interior is kept clean.
The clean box is a substantially rectangular box body opened at one surface, and has a plate-like door (i.e., lid) for closing the opening. In the case where the article to be processed such as a semiconductor wafer received in the clean box is loaded into a processing apparatus, the loading operation is performed through an additional device called a load port, mounted on the processing apparatus. The load port is a device mounted on the processing apparatus for opening and closing the lid of the clean box while keeping the clean box and the interior of the processing apparatus under the clean condition and for making it possible to transfer the article to be processed such as a semiconductor wafer housed in the clean box into the interior of the processing apparatus. The load port is sometimes called an opener because it opens the lid of the clean box.
The clean boxes are categorized into two types in accordance with the types of the associated load ports, i.e., a bottom down type which is opened at the bottom surface, for taking out the housed article in the downward direction of the box and a side open type which is opened at a side surface of the clean box for taking out the housed article in the sideway.
An example of the bottom down type clean box is shown in FIGS. 1A and 1B. FIG. 1A is a side elevational cross-sectional view of the clean box and FIG. 1B is a plan view of the lid (door).
As shown in FIG. 1A, a clean box 100 is composed of a substantially square-shaped box body 101 opened at one side surface (a bottom surface in case of the bottom down type clean box shown in FIGS. 1A and 1B) and a lid 102 for closing the opening of the box body 101. A shelf-like carrier 103 for holding the stacked semiconductor wafers to be received in the box at an equal interval is fixed above the lid 102 in the example shown in FIGS. 1A and 1B. A flange portion 101a expanded outwardly is provided around the bottom surface opening of the box body 101 into which the lid 102 is inserted/engaged.
An annular groove 110 for vacuum suction is formed in a circumferential edge portion of the surface (upper surface) facing the box body 101 of the lid 102 in the example shown in FIGS. 1A and 1B. O-rings used as elastic seal members are mounted along the inside and the outside of the annular groove 110 along the annular groove 110, respectively. Under the condition that the lid 102 closes the opening of the clean box body 101 in FIG. 2, the suction space formed by the annular groove 110 and the flanged portion 101a of the box body 101, i.e., a space of an interior of the annular groove 110 closed at its upper portion by the flanged portion 101a of the box body 101 is evacuated to thereby suck the lid 102 to the box body 101. The evacuation is performed from the back side of the lid by a means (not shown) through a gas passage 112 provided in communication with the annular groove 110. For instance, the vacuum suction method using such a suction groove is described in Japanese Patent Application Laid-Open No. 10-321696.
In such type clean box, there is provided a mechanical latch for preventing the falling off of the lid since there is a fear that the lid would be fallen off in the case where the vacuum suction is broken down due to leakage at the seal portion or the like.
Also, in a conventional clean box where the above-described vacuum suction groove is not provided, a seal member such as an O-ring is mounted so as to surround the opening of the box on the lid 102 or the box body flange portion 101a. Also in this case, although the latch mechanism for latching the lid to the box body is provided, the function of the latch mechanism is not only to prevent the lid from falling off but also to fix the lid to the body under the sealed condition by depressing the lid to the box body and deforming the seal member (O-ring) between the box body and the lid.
An example of the conventional lid latch mechanism to be used for both the clean box provided with the above-described vacuum suction annular groove and the clean box provided with no annular groove is shown in FIG. 2. FIG. 2 is a bottom view of the lid of the clean box 100 shown in FIGS. 1A and 1B.
The latch mechanism has a circular rotary cam plate 201 provided rotatably substantially at a center of the interior of the lid 102. Two cam grooves 201a and 201b are formed in the rotary cam plate 201. The latch mechanism also has slidable latch members 203 and 204. The latch members 203 and 204 are slidable up and down under the guidance of guide members 206 and 207. Cam pins 205 and 206 are implanted in the latch members 203 and 204, respectively, and the cam pins 205 and 206 are engaged with the cam grooves 201a and 201b of the rotary cam plate 201, respectively.
As shown in FIG. 2, the respective cam grooves 201a and 201b are formed into a shape such that a distance from the center of the rotary cam plate 201 is changed depending on the circumferential position thereof. The latch members 203 and 204 are moved up and down in FIG. 2 in response to the clockwise and counterclockwise rotation of the rotary cam plate 201 in accordance with the cam shape. Thus, in response to the rotational position of the rotary cam plate 201, the respective tip end portions 203a and 204a may take positions retracted and projected with respect to the circumference of the lid 102.
In the case where the lid is mounted on the clean box body 101, when the rotary cam plate 201 is rotated in the counterclockwise direction of FIG. 2 so that the tip end portions 203a and 204a of the latch members are projected from the circumference of the lid 102, the tip end portions are engaged with tabs or holes (not shown) formed in the clean box body 101 to thereby latch the lid 102 to the clean box body 101. Inversely, when the rotary cam plate 201 is fully rotated clockwise, the latch members 203 and 204 are slid to the innermost position indicated by two-dot-and-dash lines in FIG. 2. In this case, the tip end portions 203a and 204a of the latch members are retracted from the circumference of the lid to thereby release the engagement with the clean box body.
A latch drive portion 209 is provided at the center of the rotary cam plate 201 for rotatably driving the cam plate 201. A pair of circumferential holes 201c are formed in the latch drive portion 209.
A mechanism for opening/closing the above-described latch is provided in the load port for transferring the article to be processed within the clean box to the processing apparatus. A latch opening/closing mechanism having two pins that engage with the circumferential holes 201c of the above-described latch drive portion 209 of the latch mechanism is provided in the load port table on which the clean box 100 is laid on the load port. The pins are driven to rotate the latch drive portion 209 to thereby open/close the latch of the clean box lid 102.
The above-described conventional lid latch mechanism has the following disadvantage. First of all, the mechanism is complicated and needs a large number of mechanical parts. Accordingly, the cost is increased, and on the other hand, the possibility of breakdown is increased so that the operation would frequently be discontinued. Also, when the latch mechanism is to be closed and opened, a mechanism for opening/closing using a power of a motor, an actuator or the like is required (the latch opening/closing mechanism provided in the load port in the above-described conventional example). Also, this requires the increased cost and increases the possibility of breakdown due to its complicated structure.
Accordingly, there is a high demand to latch the lid to the clean box with a simpler mechanism.
An object of the present invention is to provide a lid latch mechanism for a clean box, which has a simple structure for solving the above-noted defects. According to the present invention, there is provided a lid latch mechanism for latching a lid of a clean box having a box body opening at one surface and the lid for closing the opening, comprising: a latch member that is mounted on the box body and pivotal about a single shaft; a latch engagement portion provided on the lid for engaging the latch member in its predetermined pivotal position; and a biasing member for biasing the latch member toward the latch engagement portion, wherein a guide surface is provided on a portion, facing the outside of the opening of the box body of the latch member, and when the clean box is set on a load port, the guide surface is brought into contact with and pressed by a latch guide provided on the load port so that the latch member pivots to thereby release the latch of the lid.
Also, according to the present invention, there is provided a lid latch system for a clean box in a clean transfer system composed of the clean box having a box body opening at one surface and a lid for closing the opening and a load port for opening the clean box and loading into a clean apparatus an article to be transferred within the clean box, comprising: a clean box latch mechanism including a latch member that is mounted on the box body and pivotal about a single shaft, a latch engagement portion provided on the lid for engaging the latch member kept in a predetermined pivotal position, and a biasing member for biasing the latch member toward the latch engagement portion; and a latch guide mechanism as a projection provided on the load port, wherein when the clean box is set on the load port, the latch member is brought into contact with and pressed by the latch guide mechanism so that the latch member pivots to release the latch of the lid.
In the lid latch mechanism for the clean box and the lid latch system according to the present invention, it is possible to use a structure in which upon dismounting the clean box from the load port, the pressure of the latch mechanism by the latch guide on the load port is released, and then the latch member is forced by the biasing member to pivot to thereby engage with the latch engagement portion of the lid so that the lid is automatically latched.
It is preferable that the latch mechanism be provided in each of two opposite sides of the opening of the box body.
In the lid latch mechanism for the clean box and the lid latch system according to the present invention, it is preferable to use a lid latch mechanism for such a type clean box that the clean box has an annular groove formed so as to surround the opening in at least one of the box body and the lid, so that a vacuum suction annular space is formed between the box body and the lid in a condition where the lid closes the opening of the box body.